This invention relates to the field of electric heating, and particularly to improved means for heating the liquid in stock watering tanks. Such tanks are located in the open, and are subject by rough treatment by the stock being watered. While water must be kept available, during cold weather, by supplying heat to the system, the same adverse conditions apply to any electrical equipment used for that purpose. The equipment must therefore be as rugged as possible, and should also be readily removable to a less trying storage location when heat is no longer needed.
As in most electric heating applications, reasons of economy and efficiency dictate using a heater capable in continuous use of supplying the maximum heat requirements, and providing a thermostat to observe the water temperature and turn the heater off except when the temperature drops below a predetermined point.
Experience has taught that anything hanging or projecting into a stock watering tank has an intolerably short life. Heaters have been developed which are capable of functioning when secured to the outside of the tank bottom in heat exchange relation thereto, in which location they are largely protected from physical damage, and surface thermostats are also known which can give sufficiently exact response to the temperature of the water as conducted through the tank to its outer surface. Good thermal contact is of course necessary in both cases.